1. Field of the Invention
The present invention relates to a receiver for a wireless communication system and a control method thereof; and, more particularly, to an apparatus for reducing power consumption of a receiver in a high-speed wireless communication system and a control method thereof.
2. Description of Related Art
In general, a wireless communication system enables wireless terminals to communicate without the limitation of mobility by transmitting data using a predetermined frequency. Such a wireless communication system has been continuously advanced. Recently, various high-speed wireless communication systems were introduced. A wireless terminal of such a wireless communication system performs wireless communication using a battery for eliminating the limitation of mobility. Since the wireless terminal has a limited power capacity due to the battery, many studies have been made to reduce power consumption of a wireless terminal. In case of a wireless terminal such as a Personal Digital Assistant (PDA), a mobile phone, and a laptop computer in support of a wireless Local Area Network (LAN), a wireless communication interface and a receiver consume the most of power.
A wireless terminal uses a wireless MODEM to communicate. Therefore, a maximum operation frequency was designed to be low in a physical (PHY) layer of a wireless MODEM in order to reduce power consumption of a wireless terminal. Also, a wireless MODEM is designed to have a minimum supply voltage or to have low complexity to reduce power consumption. Furthermore, a method of dynamically controlling a clock frequency and a supply voltage depending on processing load was introduced in order to reduce the power consumption.
However, there is limitation in reducing an operation frequency, minimizing a supply voltage, and reducing complexity due to the limitation of semiconductor fabrication technology. There is also a limitation in satisfying performance requirements of a system because there is a trade-off relation between the three elements for reducing the power consumption and performance.
As another method for reducing the power consumption of a wireless terminal, a method of controlling a mode of a Medium Access Control (MAC) layer has been studied to reduce energy. That is, such a MAC layer mode control method provides an active mode and a sleep mode. The active mode is a mode for waking up a wireless terminal only when a wireless terminal has data to exchange with the other party using an additional control signal that is exchanged with the other party at a regular interval. The sleep mode is a mode for making a wireless communication terminal not to use power when the wireless communication terminal does not have any data to exchange with the other party using an additional control signal exchanged with the other party at a predetermined interval.
Hereinafter, a mode based power consumption control method will be described. A wireless communication terminal has to be in an active mode all the time because the wireless communication terminal cannot predict when to receive data from the other wireless terminal although the wireless communication terminal knows when to transmit data. Since the wireless communication terminal has to be in the active mode all the times, the wireless communication terminal consumes a large amount of power although the wireless communication terminal does not transmit or receive data. Therefore, the wireless communication terminal enters to a sleep mode when the wireless communication terminal exchange messages with a transmitter and expects not having data to transmit or receive based on the message. When a wireless terminal needs to exchange data during the sleep mode, or at a predetermined time, the wireless terminal enters to the active mode.
In general, a control signal has a comparatively long time interval due to MAC layer hardware and software interruption problem. Therefore, there is limitation in using a sleep mode in a MAC layer due to trade-off relation between service quality such as throughput and delay and power consumption.
Accordingly, it has been demanded to develop a method for reducing power consumption of a wireless terminal in a wireless communication system.